Control for mixing fluids of different specific gravity

ABSTRACT

A hydrometer-actuated control for mixing dampening fluid comprising water and other chemical ingredients mixed with alcohol to be applied to the plate of a lithographic printing press. The control device comprises a mixing chamber, in which alcohol and dampening fluid are mixed, adapted to remove air bubbles therefrom; a test chamber having a hydrometer freely floating in a sample solution drawn from the mixing chamber; and an electrical conductor on the hydrometer which moves with the hydrometer relative to the surface of the sample solution to actuate a relay to open and close a solenoid operated valve to regulate flow of alcohol to the mixing chamber.

United States Patent 3,154,950 11/1964 Hargensetal..............l.3,485,257

[72} lnventor EdwinH.Royse 4740 Vicksburg St., Dallas, Tex. 75207 821,873

12/1969 Gegenheimer et al.

[21] Appl. No. Primar 1 y l:xammer-Wi1l|am F. O Dea ii Sf'f t d a :5 2Assixtan! Examiner-David J. Zobkiw I 1 en 6 AtlorneyH0ward E. Moore NT[54] f rgi FLUIDS 0F DIFFERE ABSTRACT: A hydrometer-actuated control formixing dam- 19 Claims 8 Drawin Fi S pening fluid comprising water andother chemical ingredients g g mixed with alcohol to be applied to theplate of a lithographic printing press. The control device comprises amixing chamber, in which alcohol and dampening fluid are mixed, adaptedto remove air bubbles therefrom; a test chamber having a hydrometerfreely floating in a sample solution drawn from the mixing chamber; andan electrical conductor on the hydrometer which moves with thehydrometer relative to the surface of the sample solution to actuate arelay to open and close a solenoid operated valve to regulate flow ofalcohol to the mixing chamberv 2,320,720 6/1943 l37/9lX IOGH CONTROL FORMIXING FLUIDS OF DIFFERENT SPECIFIC GRAVITY BACKGROUND OF THE INVENTIONIn a dampening device for transferring dampening fluid to the plate of alithographic offset printing press, a pan roller is rotated throughdampening fluid in a pan and a film of fluid on a pan roller istransferred to the printing plate.

US. Pat. No. 3,259,062 to Harold P. Dahlgren teaches that a watersoluble, volatile, organic liquid, such as a volatile alcohol mixed withwater is a very effective dampening fluid for use in lithographicprinting. However, the volatile fluid, exposed to the atmosphere,evaporates readily and the optimum ratio of alcohol to water isdifficult to maintain in the system.

U.S. Pat. No. 3,352,317 to Harold P. Dahlgren on Dampening Fluid CoolingAnd Circulating Apparatus For Lithographic Offset Press DampeningDevice" teaches that when a new batch of volatile fluid is added to thefountain of a dampening system to be circulated through the pan, thefluid does not readily mix with the dampening fluid therein. The addeddampening fluid changes the proportions of the ingredients of thedampening fluid, which changes the chemistry thereof, and will thereforeaffect the quality of the printing produced by the press until suchdampening fluid has become thoroughly mixed, which usually requires aconsiderable length of time. The said patent also points out that thetemperature of the dampening fluid should be maintained below 75 toprevent emulsification of the dampening fluid with the ink and to reduceoxidation of the plate which is contacted by the dampening fluid.

The objects of the devices disclosed in the before-mentioned patentswere to provide an improved dampening fluid with storage and circulationsystem which diffuses and mixes the dampening fluid and to maintain thetemperature of the dampening fluid at a predetermined optimum value. Themethod and apparatus described therein is a significant improvement overthe prior art. However, the devices did not include means forautomatically regulating the specific gravity of the dampening fluid tocompensate for ingredients of the fluid which are depleted and forevaporation of volatile fluid from the dampening fluid as the fluid wascirculated through the system. The device may also be employed toreplace any fluid which is depleted or consumed in use.

No simple device heretofore developed had the capability ofautomatically injecting desired amounts of volatile fluid into thedampening fluid for accurately maintaining the specific gravity of thedampening fluid within reasonable limits.

Specific gravity regulating apparatus heretofore developed haveattempted to use a hydrometer floating in liquid to actuate devices forcontrolling specific gravity of the liquid. However, these devices haveprovided an imperfect solution to the problem because attempts have beenmade to employ force exerted by the hydrometer to close contacts inelectrical circuits through various mechanical arrangements.

No hydrometer actuated control device heretofore developed has employeda freely floating hydrometer to automatically control the specificgravity of the liquid in which it is floating.

A hydrometer is a very sensitive instrument, the accuracy of which ismaterially affected by application of external forces thereto.

High flow rate of fluid through a chamber or receptacle in which thehydrometer is floating affects the depth to which the instrument sinksin the liquid.

Air bubbles in the liquid being tested also adversely affect theaccuracy of a hydrometer.

Another major difficulty encountered heretofore has resulted from thefact that the sample solution being tested was drawn from a relativelylarge reservoir and fluid was injected directly into the large reservoirof fluid. In such devices, an excessive amount of fluid is injected intothe reservoir before a control system, sampling the reservoir solution,detects a change therein, particularly in situations where the fluidbeing injected and the fluid in the reservoir do not mix readily.

SUMMARY OF THE INVENTION 1 have developed a device for controlling thespecific gravity of dampening fluid or other liquids which employs afreely floating hydrometer. Air bubbles are removed-from a sample of theliquid and low velocity flow is maintained during testing to providemaximum accuracy.

A primary object of the invention is to provide a control for mixingdampening fluid which uses a hydrometer for controlling the specificgravity of the fluid wherein no appreciable external force is exertedupon the hydrometer.

Another object of the invention is to provide a control for mixingdampening fluid in which fluid injected into fluid circulating from areservoir is thoroughly mixed in a mixing chamber and a sample of theresulting solution is immediately tested thereby eliminating thepossibility that excessive amounts of fluid will be injected into thereservoir solution.

A still further object of the invention is to provide a control formixing dampening fluid particularly adapted for use in combination witha dampening fluid cooling and circulating apparatus for lithographicoffset press dampening devices.

A still further object of the invention is to provide a control formixing dampening fluid incorporating a venturi in a fluid circulatingsystem for drawing a second fluid into the fluid normally circulatedthrough the system.

A still further object of the invention is to provide a control formixing dampening fluid having a high degree of accuracy, which isadjustable and inexpensive to construct and use, making the use thereofeconomically feasible.

Other and further objects of the invention will become apparent uponreferring to the specification and drawings annexed hereto.

DESCRIPTION OF THE DRAWINGS Drawings of the preferred embodiment of theinvention are provided so that the invention maybe better and more fullyunderstood, in which:

FIG. 1 is a diagrammatic view of the invention illustrating thecooperative relationship between the control device and dampening fluidcooling and circulating apparatus;

FIG. II is a top plan view of the invention with parts away to moreclearly illustrate details of construction;

FIG. III is a cross-sectional view taken along lines Ill-Ill of FIG. II;

FIG. IV is a cross-sectional view taken along lines IV-IV of FIG. III;

FIG. V is a perspective view of the back of the control device withparts broken away to more clearly illustrate details of construction;

FIG. VI is a cross-sectional view taken along lines VI-VI of FIG. Ill;

FIG. VII is a cross-sectional view taken along lines VII-VII of FIG.Ill; and

FIG. VIII is a diagrammatic view of a modified form of the invention.

Numeral references are employed to indicate the various parts shown inthe drawings and like numerals indicate like parts throughout thevarious FIGS. of the drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. I of thedrawings, the numeral 1 generally designates the body of the controldevice having a tubular mixing chamber 2 and a-tubular control or testchamber 4 connected by a passage 6.

One end of conduit 10 is connected to a circulating system 8 throughwhich electrically conductive fluid circulates as will be hereinaftermore fully explained and the other end of conduit 10 is connected to aventuri 12. A conduit 14, connected through normally closed valve 16 andconduit 15, communicates with fluid supply source 18 such that whenvalve 16 is broken opened fluid is drawn from supply source 18 throughconduit 14 by the partial vacuum at the throat of venturi 12.

The outlet of venturi l2 communicates with inlet 20 of mixing chamber 2.I

An overflow tube 22 in mixing chamber 2 has its lower end connectedthrough outlet 24 to a conduit 26 which returns fluid to the reservoir101 of circulating system 8.

A test chamber outlet passage 30 communicates with the inside of testchamber 4 at a position slightly below the elevation of the upper end ofoverflow tube 22 in mixing chamber 2. Crossover passage 6 between mixingchamber 2 and test chamber 4 is of smaller diameter than test chamberoutlet passage 30 to maintain the fluid level in test chamber 4 at'asubstantially constant elevation.

From the foregoing it should be readily apparent that a portion of thefluid flowing through circulating system 8 passes through conduit 10,venturi l2 and inlet 20 into ,mixing chamber 2. A major part of thefluid entering mixing chamber 2 flows downwardly through overflow tube22, outlet 24 and conduit 26 into the reservoir 101 of circulatingsystem 8.

A sample of the fluid in mixing chamber 2 passes through passage 6 intotest chamber 4, and through test chamber outlet 30 to be returned to thecirculating system 8.

A conventional hydrometer 40 is disposed within test chamber 4 andfloats in a sample solution contained therein.

The hydrometer is a well-known device for measuring the density orspecific gravity of liquids. It consists of a long slender glass floatweighted at the lower end and has a graduated scale on the slender neckportion such that the specific gravity of the liquid is indicated by thedepth to which the instrument sinks therein.

Anisolated solution receptacle 42 is disposed within the test chamber 4and has isolated'solution 44 contained therein. The wall 43 of isolatedsolution receptacle 42 is made of electrical insulator material and iselectrically insulated from the sample solution test chamber 4. 4 A

A conductor 46 is secured about the stem 40a of hydrometer 40 andopposite ends thereof extend into test chamber 4 and insulatedreceptacle 42 in position to contact the liquid therein.

' An electrode 50, extending through the wall of test chamber 4,issubmerged in sample solution 5 contained therein and electrode 52,extending through the wall of test chamber 4 into receptacle 42, issubmerged in the isolated solution 44 contained therein. Electrode 50 isconnected through line to a current responsive switching device, such asthe coil 56 of a single pole double throw relay 58. The-other end ofcoil 56 of relay 58 is connected through line 60 to one side of thesecondary winding 62 of a'trans former 64. Electrode 52in isolatedsolution receptacle 42 is connected through line 66 to the secondarywinding 62 of transformer 64.- i i The primary side 68 of transformer 64is connected through lines 70 and 72 to the electrical lines 74 and 76,respectively, which are connectable to a conventional source ofelectricity.

From the foregoing it should be readily apparent that when hydrometer 40sinks into sample solution 5 in test chamber 4, causing the end 47 ofconductor 4610 engagethe sample solution, an electrical circuit iscompleted from electrode 50 through the sample solution 5 in testchamber 4, through conductor 46, isolated solution 44, electrode 52,line 66, secondary winding 62, line 60, coil 56, line 54 to electrode50. Therefore, when the end 47 of conductor on hydrometer 40 engages thesurface of the sample solution 5 in testcharnber 4, coil 56 of relay 58is energized.

Line 74, connectable to an external power supply (not shown), has aswitch 78 therein. When switch 78 is closed electrical current isdelivered through lines 70 and 72 to primary winding 68 of transformer64.

Line 74 is connected to electro-magnetically actuated switch 56a ofrelay S8 in series with switch 78.

Relay 58 is of conventional design and in the particular embodiment ofthe invention illustratedin the drawing the fluid in fluid supply source18 is alcohol having a specific gravity lower than that of the fluidwhich flows through circulating system 8.

Movable pole 56a of relay 58 is spring biased to the closed position sothat alcohol will flow from fluid supply source [8 when the specificgravity of'the fluid flowing through circulating system increases,causing hydrometer 40 to move upwardly, disengaging the end 47 ofcontact 46 from the surface of the sample solution 5 in'test chamber 4.When a sufficient quantity of alcohol has been added hydrometer 40 willsettle in the sample solution, causing end 47 of contact 46 to engagesample solution 5, completing a circuit, energizing coil 56 of relay 58,thereby opening switch 56a to stop the flow of alcohol.

Lines 74' and 76 are connected to solenoid device 80 which is operablyconnected in conventional manner to valve 16.

It should be appreciated that when switch 78 in line 74 is closed andswitch 56a of relay 58 is closed a circuit is completed through solenoiddevice 80. to line 76 to open valve 16. When valve 16 is opened fluid isdrawn from container through line 14 into venturi 12 to be mixed withthe fluid flow ing through circulating system 8 in line 10.

A pilot light 82 is connected to lines 74' d 76 through lines 83 and 84,respectively, in parallelwith solenoid 80. Pilot light 82 is illuminatedwhen solenoid 80 is energized, thereby indicating that valve 16 is openand that fluid is flowing from supply source 18.

Referring to FIG. V of the drawing, the body 1 of the control device ispreferably cast or molded as an integral unit, having mixing'chamber 2,test chamber 4, passage 6, venturi l2, inlet passage 20 outlet passage24, and test chamber outlet passage 30'formed in thebody l of thecontrol device by positioning suitable cores within a mold to be filledwith molten material such as polyester resin.

While it is not absolutely necessary that the body 1 of the controldevice be cast as an integral unit having passageways formed therein, itis desirable to do so for several reasons. It should also be noted thatwhile it is not absolutely necessary that the body 1 be constructed ofmaterial which is an electrical insulator, such construction offersseveral material advantages.

Casting body I as an integral unit minimizes leakage of fluidwhich iscirculated therethrough and reduces construction costs resulting fromsavings in' material and labor. it is also desirable that the walls ofmixing chamber 2 and control chamber 4 be transparent, allowing visual'inspection of the operation of the device.

' Construction of the body I of a material which is a good electricalinsulator assures that electrical current cannot flow from electrode 50in mixing chamber 4' to electrode 52 in isolated solution receptacle '42except through conductor 46 when the end 47 thereof is in contact withthe sample solution in test chamber 4. A short circuit between electrode50 and electrode 52 makes the device inoperable. 1f the body 1 of thecontrol device is constructed of a material which is a conductor ofelectricity insulation 43 must be provided as illustrated in FIG. llI.

it is desirable that passage 6 connecting mixing chamber 2 and testchamber 4 have a smaller cross-sectional area than overflow tube 22 andtest chamber outlet passage 30. i

As best illustrated in FIG. Vll, fluid entering the control devicethrough conduit '10 circulates through inlet 20 into mixing chamber 2.The end of inlet passage 20 is substantially tangentially disposedrelative to the inner surface of tubular mixing chamber 2 which impartsa churning, agitating motion to the fluidtherein to thoroughly mix thefluids from conduits l0 and 14. Centrifugal force of the swirling liquidcauses air bubbles to be moved toward the center of the chamber allowingthem to move upwardly through the liquid about tube 22 away from passage6.

Fluid which passes through passage 6 is thoroughly mixed and is free ofair bubbles. The flow rate of liquidthrough passage 6 is small relativeto the flow rate of liquid through inlet '20. The majority of the liquidentering mixing chamber 2,

through inlet 20, is discharged through overflow tube 22. For example,diverting percent of the fluid which enters mixing chamber 2 into testchamber 4 through passage 6 will normally provide adequate solution forsampling without causing excessive turbulence to disturb the freefloating condition of hydrometer 40.

The percentage of fluid to be diverted through passage 6 into testchamber 4 may vary depending upon the flow rate of fluid throughcirculating system 8 and the quantity of fluid passing through conduit10. A primary consideration governing the flow through the test chamberis to maintain forces of the fluid on the hydrometer resulting frommotion of the sample of fluid within desired limits.

It is desirable that control chamber outlet passage 30 be larger thanpassage 6 to assure that the surface of the sample solution in controlchamber 5 be maintained substantially constant. A tubular restrictor 41extends upwardly from the bottom of control chamber 4 to disperse thejet of liquid flowing into the control chamber to minimize the forceexerted by the liquid on hydrometer 40.

Conductor 46, best illustrated in FIG. [11, may be constructed of anysuitable material which is a good conductor of electricity. However, tominimize interference with the freely floating condition of hydrometer40 it is desirable that conductor 46 be very lightweight. In theparticular embodiment of the invention illustrated in the drawing,conductor 46 is a very thin wire. The ends 47 and 47a of conductor 46are substantially vertical and of substantially uniform cross section tominimize interference with vertical movement of the hydrometer.

lt is desirable that conductor 46 be constructed of material which ishighly resistant to chemical action. A conductor plated with noblemetals, such as gold, exhibits the desired qualities.

The weight of conductor 46 must be taken into consideration whenhydrometer 40 is calibrated because hydrometer 40 will sink deeper intothe liquid with the conductor attached thereto than it would if theconductor were not attached. For example, to maintain the specificgravity of the solution in test chamber 4 at .970 the end 47 ofconductor 46 must be set at .968 if the weight of the conductor variesthe hydrometer reading .002.

It should be readily appreciated that no power is required to open andclose the circuit between the solution 5 in test chamber 4 and the end47 of the conductor 46. As hydrometer 40 moves upwardly as the specificgravity of the fluid increases, the end 47 of the conductor movesupwardly relative to the surface of the liquid until the end of the thinwire is withdrawn therefrom, breaking the electrical circuit, thusdeenergizirig coil 56 of relay 58, causing switch 56a to be closed,thereby opening valve 16 allowing alcohol to be drawn through venturi 12into the solution, reducing the specific gravity thereof. The effect ofsurface tension of the liquid on the wire is negligible.

It should be readily apparent to a person having ordinary skill in theart that if it is desired to maintain the specific gravity of the samplesolution in test chamber 4 above a desired F 16., the control devicehereinbefore described may be utilized with minor modification. A liquidhaving a specific gravity greater than that of the fluid flowing throughthe circulating system 8 may be placed in fluid supply source 18. Theonly other change required of the system is to cause switch 56a of relay58 to close as the end 47 of conductor wire 46 engages the samplesolution in test chamber 4 by spring biasing the switch 560 open. Thismay be accomplished by connecting line 74' to the normally open contact56d instead of the normally closed contact 56c of relay 58. Suchmodification would be within the skill of a person having ordinary skillin the art and further description thereof is not deemed necessary.

As hereinbefore pointed out the above described control system isparticularly adaptable for use as a control device for automaticallymaintaining a desired specific gravity of dampening fluid used inlithographic printing. The relationship of the control device to thecirculating and refrigeration system of a lithographic printing press isillustrated in FIG. I of the drawing.

A dampening fluid tank or reservoir 101 is provided, having heatinsulation 102 in the walls thereof. A quantity of dampening fluid 103may be conventional type of dampening fluid, which usually consists of amixture of chemical ingredients in water, or it may be water and otherchemical ingredients mixed with alcohol, as it is used with thedampening device disclosed in U.S. Pat. No. 3,168,037 to Harold P.Dahlgren. The level of the dampening fluid 103 is maintained above theimpeller 104 of the pump 105. The impeller 104 is rotated through ashaft 1060 by an electric motor 106 mounted on the top of the reservoir101. The impeller 104 picks up dampening fluid from the container 101through the intake opening a in the lower wall of the pump housing.

The dampening fluid is forced through the discharge line 107 and ispassed through a refrigerator unit 108 which has the usual compressor,condenser, receiver, filter and dryer, expansion valve and evaporatorcoils therein. Discharge line 107 is connected to a pipe 109 whichpasses adjacent to the evaporator coils of the refrigeration unit, andas the dampening fluid passes therethrough, it is cooled. Thetemperature of the refrigeration unit may be maintained by a suitablethermostat control (not shown).

A portion of the refrigerated dampening fluid is passed from the pipe109 through a hand operated valve 111 and a supply line to the dispenserpipe 118 which is disposed in the dampening fluid pan or fountain 115.

A branch line 112 communicates with the upper part of the reservoir 101through a discharge nipple 114.

A return hose 126 is attached to the outlet drain nipple through whichdampening fluid may return from the pan 115 to the reservoir 101. Thehose 126 communicates with a drain back pipe 128 in the reservoir 101through a suitable nipple 127 passing through the upper wall of thereservoir 101. The drain back pipe 128 is connected in communicationwith a T- fitting 129.

A restrictor nozzle 130 is connected between an outlet from thedischarge conduit 107 and the T-fitting 129. A venturi 132 is connectedto an outlet of the T-fitting- 129 opposite the restrictor nozzle 130. Aventuri discharge line 133 is connected to the opposite end of theventuri 132 and terminates at the bottom of the reservoir 101.

Dampening fluid circulating through supply line 110 into pan 115 isexposed to the atmosphere and the alcohol evaporates therefrom, changingthe chemical composition of the dampening fluid, which results in areduction of the quality of printing.

A T-fitting 10a is positioned in supply line 110 or branch line 112 fordirecting a portion of the fluid flowing therethrough through conduit 10to the control device as hereinbefore explained.

Outlet conduit 26, which communicates with overflow tube 22 in mixingchamber 2 of the control device, extends through a suitable nipple 27passing through the upper wall of the reservoir 101.

In multicolor printing a separate dampening fluid circulating system isnormally used for the dampening system of each printing station.Therefore a conventional electrical outlet socket 79 is connectedthrough lines 79a and 79b to lines 76 and 74 to facilitate connecting aseries of control devices to a single source of electricity. Lines 74and 76 of a second control device (not shown) may be connected to outlet79 of the first control device.

The operation and function of the device hereinbefore described is asfollows:

A portion of the dampening fluid 103 flowing through circulating system8 is diverted through conduit 10 into mixing chamber 2 in the body 1 ofthe control device. A portion of the dampening fluid flows into controlchamber 4 through passage 6 and the specific gravity of the dampeningfluid is automatically tested by hydrometer 40 having a conductor 46 onthe upper end thereof.

If alcohol has evaporated from the dampening fluid causing the specificgravity of the dampening fluid to be too high, the end 47 of conductor46 will be disposed above the surface of the sample solution ofdampening fluid in test chamber 41 causing the electrical circuit to bebroken, thus deenergizing relay 58 causing switch 56a to close therebyopening valve 116, allowing dampening fluid to flow from fluid supplysource 18 as the result of the vacuum lift created at the throat ofventuri 12.

Alcohol is thus automatically added to the system as required and isthoroughly mixed with fluid already in the system before being testedand released into the system.

Although this device has been disclosed primarily for automaticallymixing alcohol with dampening fluid for use in lithographic printing itwill be understood that it is useable for mixing any two fluids ofdifferent specific gravity.

In certain applications it may be desirable to control specific gravityof a solution which is not a good conductor of electricity. if thesolution in control chamber 4 is nonconductive a circuit will not becompleted between electrodes 50 and 52 when conductor 46 engages thesolution therein. The embodiment of the invention illustrated in FIG.VIII of the drawing is a modified form for controlling the specificgravity of a nonconductive solution.

Control chamber 4' is identical to control chamber 4 hereinbeforedescribed except that electrode 50 is submerged in an electricallyconductive liquid 5', which is separated from the solution in controlchamber 4' by a container 5a constructed of a suitable material which isnot electrically conductive. The surface of liquid 5 is maintained atthe same level as the surface of the solution in control chamber 4' bybalancing the weight of container 5a and liquid 5' with buoyant forceexerted thereon by liquid in the control chamber. If the surface of thesolution in control chamber 4' is maintained at a constant levelcontainer 5a may be secured to the wall of the control chamber in thesame manner as isolated solution receptacle 42'.

From the foregoing it should be readily apparent that when line 66'isconnected to transformer 64 and line 54' is connected to relay 58 ashereinbefore described with respect to the embodiment of the inventionillustrated in FIG. I of the drawing, that a circuit is completed fromcontact 52 through conductive liquid 44', conductor 46', conductiveliquid 5, contact 50', conductor 54 to the transformer 64 and relay 56as the end 47' of conductor 46 engages the surface of liquid 5' incontainer 5a. The operation of the remainder of the system hereinbeforedescribed with respect to the first embodiment remains unchanged.

From the foregoing it should be readily apparent that l have developed adevice for controlling the specific gravity of a solution of two or morefluids having different specific gravities readily adaptable to systemsin which it is desirable to maintain a constant specific gravity of asolution circulated therethrough in which one of the fluids is depletedfrom the solution.

I claim:

1. In apparatus for regulating the specific gravity of a solution offirst and second liquids comprising: a control chamber; means foradmitting a solution of first and second liquids into the controlchamber; electrically actuated means for injecting the first liquid intothe solution for mixing therewith; a receptacle in the control chamber;an electrically conductive liquid in the receptacle; electricalinsulation means separating the ireceptacle from the chamber; ahydrometer freely floating in the solution in the control chamber; afirst electrode submerged in the solution in the chamber; a secondelectrode submerged in the liquid in the receptacle; an electricalcircuit connected between the electrodes; a source of electricity in thecircuit; switch means for connecting the circuit to the electricallyactuated means; and an electrical conductor mounted on the hydrometer,said conductor having ends arranged to contact the solution in thecontrol chamber and the liquid in the receptacle respectively, thehydrometer being movable upwardly in the solution in response toincrease in the specific gravity thereof to cause one of the ends tobreak contact with the liquid in which it is disposed to thereby actuatethe switch means.

2. The combination called for in claim 1 wherein the means for admittinga solution of first and second liquids into the control chamber includesa mixing chamber with means therein to mix the first and second liquidsbefore admitting the solution into the control chamber.

3. The combination called for in claim I wherein the means for admittinga solution of first and second liquids into the control chamber includesmeans for eliminating air bubbles therefrom. v

4. The combination called for in claim 1 wherein the electricalconductormounted on the hydrometer comprises a conductor having one end submergedin the liquid in the receptacle and having the other end secured to thehydrometer and arranged to contact the solution in the control chamberas the hydrometer moves vertically relative thereto.

5. The combination called for in claim 1 wherein the means for admittinga solution of the first and second liquids into the control chamberincludes a circulating system for a lithographic offset press dampeningdevice; and means for direct ing liquid from the circulating systemthrough the control chamber and back into the circulating system.

6. The combination called for in claim 1 wherein the switch meansconnecting the electrical circuit to the electrically actuated means forinjecting first liquid into the solution includes current responsiveswitching means constructed and arranged to connect the electricallyactuated means for injecting first fluid into the solution to a sourceof electricity when the electrical conductor on the hydrometerdisengages the solution in the control chamber.

7. The combination called for in claim 1 wherein the switch means forconnecting the electrical circuit to the electrically actuated means forinjecting a first liquid into the solution includes current responsivemeans constructed and arranged to disconnect the electrically actuatedmeans for injecting first liquid into the solution from a source ofelectricity when the electrical conductor engages the solution in thecontrol chamber.

8. In a control device for regulating the specific gravity of a liquidsolution comprising, a mixing chamber; a control chamber; an inlet'tothe mixing chamber for admitting liquid solution thereto; an outlet tothe mixing chamber for discharging liquid solution therefrom; means inthe mixing chamber for agitating the solution as it passes from theinlet to the outlet; a passage between the mixing chamber and thecontrol chamber; a control chamber outlet passage communicating with theinside of the control chamber above the first named passage; aninsulated receptacle in the control chamber, said receptacle having anopen upper end disposed above the control chamber outlet passage;electrically conductive liquid in the receptacle; an electrode in thereceptacle; an electrode in the control chamber; a freely floatinghydrometer in the control chamber; an electrical. conductor mounted onthe hydrometer constructed and arranged to engage both the solution inthe control chamber and the liquid in the receptacle as the specificgravity of the solution decreases to a predetermined value; electricallyactuated means for injecting a liquid having a different specificgravity from that of the solution in the control chamber into the mixingchamber; and electrical actuating means operably connected between theelectrodes and the electrically actuated means to cause the said liquidto be injected into the solution when the conductor on the hydrometermoves out of contact with the surface of the solution in the controlchamber as the specific gravity of the solution changes.

9. The combination called for in claim 8 wherein the means in the mixingchamber for agitating the solution includes an overflow tube having anopen upper end and a lower end communicating with the outlet.

10. The combination called for in claim 9 wherein the mixing chamber hasa curved inner wall and the inlet is positioned to cause fluid to flowinto the mixing chamber substantially tangent to the curvature of thewall thereof.

11. In apparatus for maintaining the density of a solution of at leasttwo liquids at a predetermined value comprising: a chamber; a solutionof liquids in the chamber; electric current responsive means for addinga liquid to the solution; a first electrode submerged in the solution inthe chamber; a receptacle; electricity conductible liquid in thereceptacle; a second electrode submerged in the conductible liquid inthe receptacle; means connected to the electrodes for energizing thecurrent responsive means when an electrical circuit is completed betweenthe first and second electrodes; a hydrometer freely floating in thesolution; and a conductor having at least two free ends mounted on thehydrometer, one of the free ends being submerged in the conductibleliquid and the other free end being positioned to move vertically withthe hydrometer relative to the surface of the solution and contact ormove out of contact with the solution depending upon the verticalposition of the hydrometer in the solution.

12. The combination called for in claim 11 with the addition of means tovary the vertical relationship between at least one end of the conductoron the hydrometer and the hydrometer.

13. In a device for automatically controlling the specific gravity of asolution of a multiplicity of liquids; a housing including a mixingchamber and a control chamber; means for circulating the solutionthrough the mixing chamber; means for admitting a portion of thesolution to the control chamber; a free floating hydrometer in thesolution in the control chamber; an electrically insulated liquidreceptacle mounted on the wall of the control chamber having an open endextending above the level of the solution therein; an electricalconductive liquid in the receptacle; means for controlling the level ofthe liquid in the mixing chamber; means for controlling the level of theliquid in the control chamber; an electric conductor sccured to thehydrometer having free ends extending into the solution in the controlchamber and the liquid in the receptacle respectively, the free end inthe solution being arranged to move out of or into contact with thesolution as the hydrometer rises or falls in the solution; an elec trodein the solution in the control chamber; an electrode in the liquid inthe receptacle; an electric circuit attached between the electrodes;means for admitting a liquid of a different specific gravity from thatof the solution into the mixing chamber, said means including acontainer for said liquid; a conduit between the container and themixing chamber, and an electrically actuated valve in the conduit; andelectrically actuated switch means in the electric circuit operablyconnected to the valve to control the opening and closing of said valveresponsive to the closing or opening of the circuit by downward andupward movement of the hydrometer in the solution in the controlchamber.

14. The combination called for in claim 13 wherein the means forcirculating the solution through the mixing chamber includes, a conduit;a venturi in the conduit, and the conduit between the container and themixing chamber communicates with the outlet to the venturi whereby fluidis drawn from the container into the mixing chamber by the drop inpressure in the venturi;

IS. The combination called for in claim 14 wherein the container islocated below the level of the solution in the mixing chamber.

16. In a device for automatically controlling the specific gravity of asolution of a plurality of fluids. at least one of which is a volatilefluid, comprising a solution container; a quantity of solution in thecontainer; a free floating hydrometer in the solution; an insulatedliquid receptacle in the container having an open upper end above thesolution; an electrically conductive liquid in the receptacle; anelectrical conductor carried by the hydrometer having contactscontacting the solution and the liquid, at least one of which isarranged to move out of contact with the liquid or solution in which itis disposed in response to the predetermined rise of the hydrometer inthe solution; and means to admit additional volatile fluid to thecontainer including a conduit for said fluid, a solenoid valvecontrolling flow through the conduit, and an electric circuit in whichthe solenoid valve is disposed which electric circuit is also in serieswith the contacts so that the circuit is opened or closed depending uponwhether the contact in the solution container is out or in contact withthe solution.

17. In a device for controlling the specific gravity of a solution offirst and second liquids, comprising: a mixing chamber; means foradmitting the solution into the mixing chamber; actuated means foradmitting first liquid into the mixing chamber to be mixed with thesolution; means in the mixing chamber for agitating the solution and thesaid first liquid; means for removing bubbles of gas from the solution;means for determining the specific gravity of the solution mixed withthe said first liquid; actuating means operably connected between theactuated means for admitting first liquid and the means for determiningthe specific gravity of the solution, said actuating means beingconstructed and arranged to maintain the specific gravity of the liquidwithin predetermined limits.

18. The combination called for in claim 17 wherein the actuated meanscomprises electric current operated valve means; and the actuating meanscomprises a hydrometer floating in the solution, switching meansactuated by the hydrometer, and an electrical circuit between theswitching means and the valve means.

19. ln a device for automatically controlling the specific gravity of asolution of a plurality of liquid ingredients the combination comprisinga container for the solution; current responsive means for adding atleast one of the liquid ingredients to the solution; an insulatedreceptacle adjacent to the container; conductive liquid in thereceptacle; a first electrode submerged in the liquid in the receptacle;a hydrometer freely floating in the solution in the container; aconductor having at least two free ends secured to the hydrometer; oneof the free ends being submerged in the liquid in the receptacle and theother end being movable into and out of contact with the solution inresponse to movement of the hydrometer; a second electrode securedrelative to the container such that an electrical circuit is completedbetween the conductor and the second electrode when the specific gravityof the solution changes to a predetermined value; and means electricallyconnected to the first and second electrodes and the current responsivemeans for adding at least one of the liquid ingredients to cause theliquid ingredient to be added when an electrical circuit is brokenbetween the second electrode and the conductor.

2. The combination called for in claim 1 wherein the means for admittinga solution of first and second liquids into the control chamber includesa mixing chamber with means therein to mix the first and second liquidsbefore admitting the solution into the control chamber.
 3. Thecombination called for in claim 1 wherein the means for admitting asolution of first and second liquids into the control chamber includesmeans for eliminating air bubbles therefrom.
 4. The combination calledfor in claim 1 wherein the electrical conductor mounted on thehydrometer comprises a conductor having one end submerged in the liquidin the receptacle and having the other end secured to the hydrometer andarranged to contact the solution in the control chamber as thehydrometer moves vertically relative thereto.
 5. The combination calledfor in claim 1 wherein the means for admitting a solution of the firstand second liquids into the control chamber includes a circulatingsystem for a lithographic offset press dampening device; and means fordirecting liquid from the circulating system through the control chamberand back into the circulating system.
 6. The combination called for inclaim 1 wherein the switch means connecting the electrical circuit tothe electrically actuated means for injecting first liquid into thesolution includes current responsive switching means constructed andarranged to connect the electrically actuated means for injecting firstfluid into the solution to a source of electricity when the electricalconductor on the hydrometer disengages the solution in the controlchamber.
 7. The combination called for in claim 1 wherein the switchmeans for connecting the electrical circuit to the electrically actuatedmeans for injecting a first liquid into the solution includes currentresponsive means constructed and arranged to disconnect the electricallyactuated means for injecting first liquid into the solution from asource of electricity when the electrical conductor engagEs the solutionin the control chamber.
 8. In a control device for regulating thespecific gravity of a liquid solution comprising, a mixing chamber; acontrol chamber; an inlet to the mixing chamber for admitting liquidsolution thereto; an outlet to the mixing chamber for discharging liquidsolution therefrom; means in the mixing chamber for agitating thesolution as it passes from the inlet to the outlet; a passage betweenthe mixing chamber and the control chamber; a control chamber outletpassage communicating with the inside of the control chamber above thefirst named passage; an insulated receptacle in the control chamber,said receptacle having an open upper end disposed above the controlchamber outlet passage; electrically conductive liquid in thereceptacle; an electrode in the receptacle; an electrode in the controlchamber; a freely floating hydrometer in the control chamber; anelectrical conductor mounted on the hydrometer constructed and arrangedto engage both the solution in the control chamber and the liquid in thereceptacle as the specific gravity of the solution decreases to apredetermined value; electrically actuated means for injecting a liquidhaving a different specific gravity from that of the solution in thecontrol chamber into the mixing chamber; and electrical actuating meansoperably connected between the electrodes and the electrically actuatedmeans to cause the said liquid to be injected into the solution when theconductor on the hydrometer moves out of contact with the surface of thesolution in the control chamber as the specific gravity of the solutionchanges.
 9. The combination called for in claim 8 wherein the means inthe mixing chamber for agitating the solution includes an overflow tubehaving an open upper end and a lower end communicating with the outlet.10. The combination called for in claim 9 wherein the mixing chamber hasa curved inner wall and the inlet is positioned to cause fluid to flowinto the mixing chamber substantially tangent to the curvature of thewall thereof.
 11. In apparatus for maintaining the density of a solutionof at least two liquids at a predetermined value comprising: a chamber;a solution of liquids in the chamber; electric current responsive meansfor adding a liquid to the solution; a first electrode submerged in thesolution in the chamber; a receptacle; electricity conductible liquid inthe receptacle; a second electrode submerged in the conductible liquidin the receptacle; means connected to the electrodes for energizing thecurrent responsive means when an electrical circuit is completed betweenthe first and second electrodes; a hydrometer freely floating in thesolution; and a conductor having at least two free ends mounted on thehydrometer, one of the free ends being submerged in the conductibleliquid and the other free end being positioned to move vertically withthe hydrometer relative to the surface of the solution and contact ormove out of contact with the solution depending upon the verticalposition of the hydrometer in the solution.
 12. The combination calledfor in claim 11 with the addition of means to vary the verticalrelationship between at least one end of the conductor on the hydrometerand the hydrometer.
 13. In a device for automatically controlling thespecific gravity of a solution of a multiplicity of liquids; a housingincluding a mixing chamber and a control chamber; means for circulatingthe solution through the mixing chamber; means for admitting a portionof the solution to the control chamber; a free floating hydrometer inthe solution in the control chamber; an electrically insulated liquidreceptacle mounted on the wall of the control chamber having an open endextending above the level of the solution therein; an electricalconductive liquid in the receptacle; means for controlling the level ofthe liquid in the mixing chamber; means for controlling the level of theliquid in the control chamber; an electric conductor secured to thehydromEter having free ends extending into the solution in the controlchamber and the liquid in the receptacle respectively, the free end inthe solution being arranged to move out of or into contact with thesolution as the hydrometer rises or falls in the solution; an electrodein the solution in the control chamber; an electrode in the liquid inthe receptacle; an electric circuit attached between the electrodes;means for admitting a liquid of a different specific gravity from thatof the solution into the mixing chamber, said means including acontainer for said liquid; a conduit between the container and themixing chamber, and an electrically actuated valve in the conduit; andelectrically actuated switch means in the electric circuit operablyconnected to the valve to control the opening and closing of said valveresponsive to the closing or opening of the circuit by downward andupward movement of the hydrometer in the solution in the controlchamber.
 14. The combination called for in claim 13 wherein the meansfor circulating the solution through the mixing chamber includes, aconduit; a venturi in the conduit, and the conduit between the containerand the mixing chamber communicates with the outlet to the venturiwhereby fluid is drawn from the container into the mixing chamber by thedrop in pressure in the venturi.
 15. The combination called for in claim14 wherein the container is located below the level of the solution inthe mixing chamber.
 16. In a device for automatically controlling thespecific gravity of a solution of a plurality of fluids, at least one ofwhich is a volatile fluid, comprising a solution container; a quantityof solution in the container; a free floating hydrometer in thesolution; an insulated liquid receptacle in the container having an openupper end above the solution; an electrically conductive liquid in thereceptacle; an electrical conductor carried by the hydrometer havingcontacts contacting the solution and the liquid, at least one of whichis arranged to move out of contact with the liquid or solution in whichit is disposed in response to the predetermined rise of the hydrometerin the solution; and means to admit additional volatile fluid to thecontainer including a conduit for said fluid, a solenoid valvecontrolling flow through the conduit, and an electric circuit in whichthe solenoid valve is disposed, which electric circuit is also in serieswith the contacts so that the circuit is opened or closed depending uponwhether the contact in the solution container is out or in contact withthe solution.
 17. In a device for controlling the specific gravity of asolution of first and second liquids, comprising: a mixing chamber;means for admitting the solution into the mixing chamber; actuated meansfor admitting first liquid into the mixing chamber to be mixed with thesolution; means in the mixing chamber for agitating the solution and thesaid first liquid; means for removing bubbles of gas from the solution;means for determining the specific gravity of the solution mixed withthe said first liquid; actuating means operably connected between theactuated means for admitting first liquid and the means for determiningthe specific gravity of the solution, said actuating means beingconstructed and arranged to maintain the specific gravity of the liquidwithin predetermined limits.
 18. The combination called for in claim 17wherein the actuated means comprises electric current operated valvemeans; and the actuating means comprises a hydrometer floating in thesolution, switching means actuated by the hydrometer, and an electricalcircuit between the switching means and the valve means.
 19. In a devicefor automatically controlling the specific gravity of a solution of aplurality of liquid ingredients, the combination comprising a containerfor the solution; current responsive means for adding at least one ofthe liquid ingredients to the solution; an insulated receptacle adjacentto the container; condUctive liquid in the receptacle; a first electrodesubmerged in the liquid in the receptacle; a hydrometer freely floatingin the solution in the container; a conductor having at least two freeends secured to the hydrometer; one of the free ends being submerged inthe liquid in the receptacle and the other end being movable into andout of contact with the solution in response to movement of thehydrometer; a second electrode secured relative to the container suchthat an electrical circuit is completed between the conductor and thesecond electrode when the specific gravity of the solution changes to apredetermined value; and means electrically connected to the first andsecond electrodes and the current responsive means for adding at leastone of the liquid ingredients to cause the liquid ingredient to be addedwhen an electrical circuit is broken between the second electrode andthe conductor.